1. Field of the Invention
The present invention relates to data dissemination between peers in a peer-to-peer (or “P2P”) wireless environment.
One means here by “peer” a wireless communication equipment capable of exchanging data (or symbols (i.e. blocks or packets or chunks of data)) with other peers or network equipments in a P2P mode through wireless communications and by means of a distributed adaptive or reactive protocol. So, a peer may be a laptop, a smartphone, a mobile or cellular telephone, a personal digital assistant (PDA), provided that it comprises a wireless communication interface (or any equivalent wireless communication means), or a node associated to a vehicle (for instance a bus or a car) or a base station that is assisting opportunistic data delivery in an area (such as a content “booth” (or a “throwbox”)).
Moreover, one means here by “data dissemination” the transmission of data between peers in order each of these peers had these data at its disposal or at the disposal of other peers.
More, one means here by “data” any group or set of digital data that can be disseminated in a P2P mode, and notably contents (such as files of information data, videos, chunks of video, pictures to share, html files, audio files or software updates), and values of parameters or counters.
2. Description of the Prior Art
The number of wireless communication equipments (and notably mobile telephones, smartphones and portable equipments), capable of displaying, storing, transmitting, and more generally using, data, is increasing, and the operators of wireless communication networks are facing a main issue: how to disseminate the data efficiently between wireless communication equipments.
Today, most of the wireless data dissemination applications proceed to content dissemination by means of a direct transmission through a centralized infrastructure. However, this solution is both expensive for the content provider and inefficient from a networking perspective as it leaves unused the potentially very large quantity of bandwidth which is available for data exchange between wireless communication equipments within short range radio transmission (e.g. Bluetooth or IEEE 802.11).
Networks that leverage local connection opportunities to communicate in a delay tolerant manner can be classified into two different categories. A first category comprises networks involving nodes with scheduled or controlled routes and using a routing protocol to communicate critical information in due time. A second category comprises networks to which wireless communication equipments with unpredictable mobility are connected, e.g. because their users are attending a conference or a common event. In the latter case, no protocol can guarantee to deliver a message within a fixed time although the performance of a peer-to-peer application can still be acceptable.
It is recalled that in a P2P environment, communication equipments (or peers) meet according to a simple homogeneous and memoryless process, as if they follow uncoordinated mobility, and have a dedicated buffer (or cache memory) which can be filled with data (such as content items (or files)) that could be requested later by other peers. The demands (or requests) for different data arise according to a stationary regime that can follow an arbitrary popularity distribution. In contrast with traditional fixed P2P networks, in wireless P2P networks the time elapsed between the demand arising and the fulfillment of this demand can be far from negligible. So, this time elapsed (or delay to fulfil a request) plays an important role in the perception of the P2P network by users. Indeed, in some cases it may happen that the interest for data (for instance a content item (or file)) becomes obsolete before the peer has any chance to receive these data.
To reduce the mean time that is necessary to a wireless communication equipment to obtain requested data (such as a content item) in a wireless P2P environment, it has been proposed to implement a distributed replication scheme consisting in creating replications of content items into peers containing these content items, when necessary. But, this replication scheme does not occur instantaneously and requires decoupling of the time when a wireless communication equipment (or node) realizes that an action should be carried out and the time when this node can effectively carry out (or execute) this action.